Missing Keyword Error in Oracle BIP Report when Using Case statement in where clause - Oracle fusion grants management query

I am trying to pull some awards attributes using BI Publisher report in Oracle Cloud Fusion - Grants Management. My query includes a field which need a arithmetic calculation and converting to a character from there,

My BIP Query is like the following,

  SELECT
      GMS_AWDINFO.CONTRACT_NUMBER  AWARD_NUMBER
      ,GMS_AWDINFO.CONTRACT_NAME  AWARD_NAME
      ,GMS_AWDINFO.ATTRIBUTE2 BILL_TYPE
      ,GMS_AWDINFO.STS_CODE AWARD_STATUS
      ,TO_CHAR(GMS_AWDINFO.END_DATE,'MM/DD/YYYY') AS AWARD_END_DATE
      ,(CASE 
       WHEN to_date(GMS_AWDINFO.END_DATE, 'yyyy-mm-dd') - trunc(sysdate) > 30 
         THEN 'Over 30 Days'
       WHEN to_date(GMS_AWDINFO.END_DATE, 'yyyy-mm-dd') - trunc(sysdate) between 30 and 1  THEN 'Within 30 Days'
       WHEN to_date(GMS_AWDINFO.END_DATE, 'yyyy-mm-dd') - trunc(sysdate) < 1 THEN 'Expired'
       END) AS AWARD_EXPIRATION_STATUS  
  FROM 
      GMS_AWARD_HEADERS_INFO_V GMS_AWDINFO   
  WHERE   
      GMS_AWDINFO.CONTRACT_NUMBER IS NOT NULL
      AND (GMS_AWDINFO.CONTRACT_NUMBER IN (:P_AWARD_NUMBER) OR 'ALL' IN (:P_AWARD_NUMBER||'ALL'))
     AND (GMS_AWDINFO.STS_CODE IN (:P_AWARD_STATUS) OR 'ALL' IN (:P_AWARD_STATUS||'ALL'))
     AND  (
         CASE WHEN :P_EXPIRATION_STATUS = 'Over 30 Days' 
            THEN (to_date(GMS_AWDINFO.END_DATE, 'yyyy-mm-dd') - trunc(sysdate)) > 30
         
                 WHEN :P_EXPIRATION_STATUS = 'Within 30 Days' 
            THEN  (to_date(GMS_AWDINFO.END_DATE, 'yyyy-mm-dd') - trunc(sysdate)) between 30 and 1

                 ELSE (to_date(GMS_AWDINFO.END_DATE, 'yyyy-mm-dd') - trunc(sysdate))  < 1
                 END 
       )
     
  GROUP BY 
       GMS_AWDINFO.CONTRACT_NUMBER 
      ,GMS_AWDINFO.CONTRACT_NAME  
      ,GMS_AWDINFO.ATTRIBUTE2 
      ,GMS_AWDINFO.STS_CODE 
      ,GMS_AWDINFO.END_DATE

In my where clause I need to pass parameter P_EXPIRATION_STATUS variable and need to check the corresponding value after a calculation in where clause.

So here according to the value of variable, need to do checking after a calculation. And I added case statement inside where clause.

But I am getting ORA-00905: missing keyword .

I just started in oracle BIP reporting. So can anyone suggest or guide me to resolve this issue please?

Or Do I need to use any different approach here?

CASE expressions return scalar values, they do not return expressions. Just use AND and OR.

SELECT CONTRACT_NUMBER AS AWARD_NUMBER
      ,CONTRACT_NAME AS AWARD_NAME
      ,ATTRIBUTE2 AS BILL_TYPE
      ,STS_CODE AS AWARD_STATUS
      ,TO_CHAR(END_DATE,'MM/DD/YYYY') AS AWARD_END_DATE
      ,CASE 
       WHEN TRUNC(END_DATE) - trunc(sysdate) > 30 
       THEN 'Over 30 Days'
       WHEN TRUNC(END_DATE) - trunc(sysdate) between 30 and 1
       THEN 'Within 30 Days'
       WHEN TRUNC(END_DATE) - trunc(sysdate) < 1
       THEN 'Expired'
       END AS AWARD_EXPIRATION_STATUS  
FROM   GMS_AWARD_HEADERS_INFO_V
WHERE  CONTRACT_NUMBER IS NOT NULL
AND    (  CONTRACT_NUMBER IN (:P_AWARD_NUMBER)
       OR 'ALL' IN (:P_AWARD_NUMBER||'ALL')
       )
AND    (  STS_CODE IN (:P_AWARD_STATUS)
       OR 'ALL' IN (:P_AWARD_STATUS||'ALL')
       )
AND    (
          (   :P_EXPIRATION_STATUS = 'Over 30 Days' 
          AND TRUNC(END_DATE) - trunc(sysdate) > 30
          )
       OR (   :P_EXPIRATION_STATUS = 'Within 30 Days' 
          AND TRUNC(END_DATE) - trunc(sysdate) between 30 and 1
          )
       OR (   :P_EXPIRATION_STATUS NOT IN ('Over 30 Days', 'Within 30 Days')
          AND TRUNC(END_DATE) - trunc(sysdate) < 1
          )
       )
GROUP BY 
       CONTRACT_NUMBER 
      ,CONTRACT_NAME  
      ,ATTRIBUTE2 
      ,STS_CODE 
      ,END_DATE

I don't know if BI-Publisher has a pre-processor that rewrites the queries according to the contents of the bind variables, but in SQL CONTRACT_NUMBER IN (:P_AWARD_NUMBER) is identical to CONTRACT_NUMBER = :P_AWARD_NUMBER as the bind variable is treated as a single scalar value (so passing a string with a delimited list would still be one value and not a list of values - unless you have a pre-processor that changes that behaviour). Similarly, 'ALL' IN (:P_AWARD_NUMBER||'ALL') is the same as 'ALL' = :P_AWARD_NUMBER||'ALL' and would match nothing if :P_AWARD_NUMBER is set and is effectively the same as :P_AWARD_NUMBER IS NULL.